Obesity is a medical condition affecting more than 30% of the population in the United States. Obesity affects an individual's quality of life and contributes significantly to morbidity and mortality. Obesity is most commonly defined by body mass index (BMI), a measure which takes into account a person's weight and height to gauge total body fat. It is a simple, rapid, and inexpensive measure that correlates both with morbidity and mortality. Overweight is defined as a BMI of 25 to 29.9 kg/m2 and obesity as a BMI of 30 kg/m2. Morbid obesity is defined as BMI ≧40 kg/m2 or being 100 lbs. overweight. Obesity and its co-morbidities are estimated to cost an excess of $100 billion dollars annually in direct and indirect health care costs. Among the co-morbid conditions which have been associated with obesity are type 2 diabetes mellitus, cardiovascular disease, hypertension, dyslipidemias, gastroesophageal reflux disease, obstructive sleep apnea, urinary incontinence, infertility, osteoarthritis of the weight-bearing joints, and some cancers. These complications can affect all systems of the body, and dispel the misconception that obesity is merely a cosmetic problem. Studies have shown that conservative treatment with diet and exercise alone may be ineffective for reducing excess body weight in many patients.
A surgical procedure has been developed for involuting the gastric cavity wall to reduce stomach volume as a treatment for obesity. In the gastric volume reduction (GVR) procedure (e.g., reduction gastroplasty), multiple pairs of suture anchoring devices, such as T-Tag anchors, are deployed through the gastric cavity wall. Preferably, the suture anchors are deployed through a small diameter port in a minimally invasive surgical procedure to reduce trauma to the patient. Following deployment of the T-Tag anchors, the suture attached to each individual pair of anchors is cinched to approximate the tissue and secured to involute the cavity wall between the anchors. This procedure is described in greater detail in co-pending U.S. patent application Ser. Nos. 11/779,314 and 11/779,322, which are hereby incorporated herein by reference in their entirety. Procedure variations of particular interest include the case where the involution occurs about the midline of the anterior surface of the stomach, the case where the involution occurs about the greater curvature of the stomach following the removal or relaxing of attachment points along the greater curve (e.g., dissection of the omentum from the gastric wall), and combinations of these (e.g., the involution begins at the apex of the fundus about the greater curve and transitions to the anterior surface near the incisura angularis). One effect of the procedure is to more rapidly induce feelings of satiation defined herein as achieving a level of fullness during a meal that helps regulate the amount of food consumed. Another effect of this procedure is to prolong the effect of satiety which is defined herein as delaying the onset of hunger after a meal which in turn regulates the frequency of eating. By way of a non-limiting list of examples, positive impacts on satiation and satiety may be achieved by a GVR procedure through one or more of the following mechanisms: reduction of stomach capacity, rapid engagement of stretch receptors, alterations in gastric motility, pressure induced alteration in gut hormone levels, and alterations to the flow of food either into or out of the stomach. As an example, a stomach with a reduced capacity will distend more quickly for a given volume of food. This distension of the stomach may trigger stretch receptors which in turn trigger a sense of satiation. In another example, the procedure will limit the stomach's ability to expand, effectively reducing its capacity or fill volume. Additionally, the procedure may induce a beneficial hormonal effect due either to the more rapid triggering of stretch receptors in certain regions of the stomach or the prevention of hormone release by eliminating triggering mechanisms from being engaged in the infolded region that no longer experiences stretch in the same manner. In yet another example, the procedure may alter gastric emptying by preventing efficient antral contractions. Additionally, the infolded region may provide a restrictive inlet into the stomach just distal to the esophagogastric junction. The GVR procedures described in these applications require individual placement of each suture anchor pair into the cavity wall tissue, and subsequent tensioning of the suture between the anchor pairs in order to involute the tissue. This individual placement of the T-Tag anchors and manual suture tensioning is time intensive; increasing the duration, complexity and cost of the GVR procedure. Accordingly, it is desirable to have a simpler, less expensive means for forming a tissue fold within the peritoneal cavity.
It is known to use surgical staples for binding and holding body tissues together following an anastomosis, skin closure, or other surgical procedure. Traditionally, these staples have had a wide U-shape in the undeformed state, requiring a large incision site or wide diameter trocar cannula to accommodate the staples and stapler. Staples and staplers having a lower profile have been developed for use in smaller diameter (i.e. 5 mm or 10 mm) trocars. However, these devices suffer from a number of deficiencies which make them impractical for use in the GVR procedure. In particular, one such stapler requires bending the staple a full 180° from the predeployment, stacked condition in the stapler to the closed, deployed condition in the tissue. Obtaining this degree of plastic deformation requires that the staple be composed of a soft, ductile material, such as soft titanium. However, the use of a soft ductile material decreases the strength and holding power of the formed staple, thus making the staple unsuitable for the pressures associated with involuting the gastric cavity wall. Staples having a triangular prefiring configuration have also been developed for deployment through a low profile stapler. However, the triangular shape of these staples prevents the staples from being stacked and fed longitudinally through the stapler shaft. Instead, the staples are stacked and fed vertically within the stapler, which reduces the number of staples that can be deployed from the stapler while still maintaining a low profile diameter. Since some versions of the GVR procedure may require a large number of staples to involute the cavity wall, vertical stacking would necessitate using more than one stapler to complete a procedure. Additionally, previous staplers have bent staples at three or fewer points during formation and deployment, which reduces the amount of work hardening and, thus, strengthening within the formed staple.
Accordingly, to facilitate the GVR procedure it is desirable to have an improved surgical staple and deploying stapler for fastening layers of tissue within the peritoneal cavity. It is desirable that the stapler has a low profile for use through a small diameter laparoscopic port or endoscope, yet be capable of deploying staples with a large tissue purchase. Further, it is desirable that the staples have a folded, box shape, and that a large quantity of the staples be deliverable by a single stapler during a procedure. Additionally, it is desirable to have a stapler which alters the configuration of a staple from a low profile, reduced width prior to deployment to a wider, operable width following deployment. Furthermore, it is desirable that the staple be comprised of a strong material having a high yield stress, and that the forming process includes greater than 3 bending points to increase the strength of the formed staple. The present invention provides a surgical staple and stapler which achieves these objectives.